Caffeine Content in 39 Tea Samples

Caffeine is a colourless material that occurs naturally in the tea plant. The wide-spreading myths that darker colour teas have more caffeine, or the less oxidation the leaves the less caffeine are all sheer myths.

Caffeine Special Feature
Caffeine: What it does  • How Much is Safe?  • Caffeine in 39 teas

Myths

While it is true that various manners of processing do have effects on the final quantity of caffeine content, the quality of the plucks (ie the green leaves before processing) as a result of the specific tea cultivar, phrase of leaf development, pluck position, horticultural conditions, the season and the very weather during the picking have a more profound influence (1, 2). This applies to caffeine, as it does to any other tea substances.

Fact-finding

The College of Medicine of National Taiwan University did a study (1) in cooperation with the Taiwan Tea Experiment Station in Taipei to find out in details from a range of 31 tea selections what exactly the differences are. Some of these selections are the same variety on purpose. Their research covered a few things, but let’s look at the results about caffeine. The scientists have based their data on steeping the tealeaves in 100°C water for 30 minutes, so it is likely that you get less caffeine even if you are buying the very same batch of tea when you infuse it normally for drinking.

To supplement their findings for the purpose of a general idea for making decisions in real life purchase, we have also integrated the findings of another study in Beijing (3) involving 39 tea selections and another one in Massachusetts (4).

Caffeine Content of Various Teas in Water Extract

Each of the tea leaves (1 g) was extracted by 100 mL of boiling water for 30 min. Data source as in citation in note 1
*Additional data from citation as in note 3
**Additional data from citation as in note 4

Observation

A few things jump out as obvious in the chart:

  • The same variety of tea can have different levels of caffeine. For example, a sencha can have either 26mg/g or almost 32mg/g.
  • The green tea samples generally has more caffeine than other groups in the selections
  • The amount of caffeine in the green tea group vary not so much according to leaf size, but likely to region, cultivar, or other horticultural difference (5). For example, the larger leaf green tea Long’jing, which is from Taiwan, has more caffeine than the two smaller leaf samples from Zhejiang. Leaf size differences in normal leaf tea green tea production is not as huge as between tea categories. For example, the production of a number of traditional oolong, particularly Wuyi and Phoenix, normally employs much larger leaves than most green or black teas.
  • With the exception of the two new cultivar Red Cloak (Xiao Hong’pao, as different from Da Hong’pao) selections, the two oolong groups generally have lesser caffeine than other groups
  • The one sample of new tea Tieguanyin (6) has the lowest caffeine content amongst all the samples.
  • The Taiwan oolong can have 40% less caffeine upon 4 years of maturing when compared to its newer counterparts
  • A 20-year-old pu’er has more caffeine than a newer one and far more than a 4-year-old oolong
  • Grounded oolong tea and the Lipton teabag, even though they are of lesser quality, they still have very high caffeine contents relative to others in the group

Again, it is important to know that the samples above illustrate only a tiny fraction of tea varieties and they are not comprehensive enough to reflect any general principle for generalization. They are however, good to demystify many wrong perceptions. It’s also good to know that there is an example of oolong that matures to lesser caffeine, because we all love matured oolongs here.

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footnotes
1. Y. Lin et al, Factors Affecting the Levels of Tea Polyphenols and Caffeine in Tea Leaves, Journal of Agricultural and Food Chemistry 2003, 51, 1864-1873
2. P. Mohanpuria et al, Caffeine Biosynthesis and Degradation in Tea [Camellia sinensis (L.) O. Kuntze] is under Developmental and Seasonal Regulation, Molecular Biotechnology (2009) 43:104–111
3. J. Xiao et al, Determination of Polyphenols and Alkaloids in Tea and Cluster-Linear Discrimination Analysis, Shipin Keshe (食品科學) 2010, Vol. 31, No. 22 343
Unlike the Taiwan study, in this Beijing study tea substances were extracted in methanol, a kind of alcohol solvent commonly employed in other studies in tea and other subject matters. This extraction route is one of the most effective way to get the most polyphenols and caffeine contents from tea for measurement purposes. 
4. Y. Zuo et al, Simultaneous determination of catechins, caffeine and gallic acids in green, Oolong, black and pu-erh teas using HPLC with a photodiode array detector, Talanta 57 (2002) 307–316
5. This is further studied and expressed with a few experiments in the studies in the Y. Lin and the P. Mohanpuria reports cited above.
6. As detailed in the J. Xiao report cited above.

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